Update flake8 requirement from <7.0,>=6.0 to >=6.0,<8.0

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@6.0.0...7.0.0)

---
updated-dependencies:
- dependency-name: flake8
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements-dev.txt

@@ -7,7 +7,7 @@
 
 bandit[toml] >=1.0, <2.0
 black >=23.0, <24.0
-flake8 >=6.0, <7.0
+flake8 >=6.0, <8.0
 flake8-bandit >=4.0, <5.0
 flake8-bugbear >=23.0, <24.0
 flake8-builtins >=2.0, <3.0